The HIV Rev gene was discovered more than 15 years ago and has been the subject of multiple studies. We now know that the Rev protein interacts not only with the RRE, but also with the cellular machinery in a complicated export pathway that enables the efficient expression of proteins from mRNAs that contain complete introns. In spite of the great insight into these processes that have been made in recent years, much remains to be elucidated. This proposal is focused on some of the aspects of Rev/RRE function that are not well understood. The specific aims are: Aim #1: To further evaluate the importance of regions of the HIV RRE outside of stem loop II and the basis for changes in the RRE leading to RevM10 resistance. Aim# 2: To further analyze the role of the cellular protein Sam68 in Rev function. Aim#3: To analyze Rev phosphorylation and its potential role in Rev function. [unreadable] [unreadable]